Method for recovering uranium from oils



United States PatentO A lVIETHOD FOR RECOVERING FROM OILS Leon H. Gooch, Norris, Tenn., assignor to the United States of America as represented by the United States Atomic Energy Commission I V No Drawing. Application January 18, 1952 Serial No. 267,184

11 Claims. (Cl. 23-145) .r 2,894,808 Patented July 14, 1959 to these oilsand separating the resulting soliduranium values, from the resulting mixture of acetone and oil.

My method. is advantageous over prior art methods in that much better recovery may be achieved from highly contaminated oils which contain considerably more than 5,000 parts per million uranium by weight. The uranium content of the resulting separated oil is usually reduced to less than about /2 to about 5 parts per million by weight. The uranium values in the resulting cake may be' converted easily easily to UP for example, by burning and subsequent flucrination, whereas the hydroxide cake obtained in the lime-fioccing method of the'co' pending patent application referred to herein is processed to UF ith comparative ditficulty, primarily due to the extremely low ratio of uranium to alkaline earth hydrox Y ide in thecake.

Although I have indicated above that certain other organic diluents have been utilized in processes for recovering uranium from oil they were utilized merely for their diluent action. I have discovered that acetoneis uniquely outstanding for causing uranium values to resolve into a readily filterable and recoverable form. Thus,

per million to approximately 25,000 parts per million by Weight.

Various attempts have been made to remove the urani umcontained in these hydrocarbon oils in a form readily convertible to a useful compound such as UF These methods have included burning these oils and recovering the uranium oxide remaining in the residues by conventional techniques; or diluting these oils with petroleum ether or other suitable organic diluents, filtering the re sulting mixtures, and recovering as solid residues that part of the uranium which may have been dispersed in the oils in insoluble form, for example, as UF These methods were found to be unsatisfactory due to high uranium losses. In addition, co-pending patent application, Serial Number 151,301, filed March 22, 1950, by Spears P. Vavalides, entitled Removal of Uranium from Organic Liquids, discloses a method of removing uranium from neutral organic liquids, including hydrocarbon oils, which comprises slurrying these liquids with a solid alkaline earth hydroxide, separating the resulting uranium-containing solid phase from the supernatant liquid,

and recovering the uranium from the separated solid phase by conventional means. This method, however, is not entirely satisfactory for treating hydrocarbon oils containing more than about 5,000 parts per million uranium by weight. Furthermore, the separation of the small quantities of uranium contained in the separated solid phase, for subsequent conversion to useful uranium compounds such as UF is accomplished with considerable difficulty and expense.

An object of my present invention, therefore, is to provide an improved process for removing uraniumfrom hydrocarbon oils.

Another object of my invention is to provide an improved process for achieving substantially quantitative removal of uranium from highly contaminated bon'oils. A further object is to provide a process for effecting the removal of uranium from the above oils in a form economically convertible to a substantially pure uranium fluoride. 3

Additional objects and advantages of my invention will be apparent from the following description: Inaccordance with my present invention, substantially complete removal of uranium from a hydrocarbon oil may be etfeeted by adding a suitable quantity of acetone hydrocarfor example, Varsol (a petroleum fraction distilled oif above gasoline and below kerosene), carbon tetra: chloride; 'trichlorethylene and isopropyl alcohol when substituted individually for acetone in my process resulted in practically no recovery of uranium. Attempts to separate uranium values by filtration after treatment with each of these reagents resulted in only a slight brown 'stain'appearing on the filter medium. In contrast, using acetone, substantially quantitative removal of uranium in a relatively thick cake was effected from the same uranium-contaminated oil, as demonstrated hereinafter.

Although I cannot present a specific mechanism to explain the unique success of acetone in my process, it appears that acetone has an unpredictable and unusually strong associative efiect on the finely dispersed particulate and/ or colloidal forms of uranium values contained in the oil, resulting in a definite settling out or flocculation of uranium values in the mixture of acetone and oil in a readily filterable form. Heretofore, it had been believed that only a portion of the uranium in such oils existed in particulate and/ or colloidal forms and that some chemical method would be necessary to eifect quantitative recovery of uranium therefrom. However, in view of the excellent recoveries of uranium using my method, there is a strong probability that the uranium exists in the oil substantially completely in fine particle and/0r colloidal forms. It is noted here that a successful, direct filtration of these uranium-containing oils is virtually impossible due to the relatively high viscosity of the oils and the finely divided and probably partially colloidal ,nature of the uranium values.

In general, any uranium values which are present in the hydrocarbon oils in amounts ranging up to 25,000 parts per million uranium by weight and in relatively finely dispersed'particulate and/or colloidal form may be efiectively removed by my process. I have found, however, that my invention is particularly suited for the removal of halogenated uranium values, and more particularlyfor the removal-of uranium fluorides. In more detail, for example, I find that I may quantitatively remove uranium whichmay be present as substantially all UFg-and possibly as some UO F Thus, in a particular-process utilizing UF small quantities of UP may seep into hydrocarbonioils. These hydrocarbons tendto have a reducing eifect on the UF converting part or all of the UP to UF Any moisture content of the hydrocarbon oils'm'ay also react with part or all of the UF to form UO F :The above two effects may be present together of the specific hydrocarbon oil and the amountlof moisture available for reaction with the UP However, analysis of numerous samples indicates that a majorportion of the uranium from such a process is present as UF The ratio of acetone to the hydrocarbon oil being treated for uraniumremoval is not critical. However; in obtaining optimum efliciency of my uranium removal process, I generally find that less acetone is required for low initial concentrations of uranium, than for high initial concentrations. Thus, where the initial uranium concentration is of the order of 100 to 200 parts per million, I generally prefer to use approximately 1 part of acetone to to 12 parts of: oil. For an initial uranium concentration of the order of 20,000 parts per million, I generally prefer to use about 1 part of acetone to about 2 parts of oil.

I cons oils approximately one part of V arsol" to about 5 to about '10 parts of oil may result in an overall process improvement. When Varsol is used in this manner, we find that a reduction is made possible in the amount of acetone which otherwise must be utilized.

My process may be successfully used not only with hydrocarbon oils which are substantially unaltered from a chemical and physical standpoint, but is particularly successful with uranium-containing hydrocarbon oils that have been cracked by the action of strongly reactive compounds and elements such as ClF F and UP until they appear as tarry, greasy residues. In these instances,

, the use of a diluent such as Varsol, as herein described, is highly advantageous, and excellent uranium recoveries The acetone needs to be agitated together with the hydrocarbon oil only for as long as is required to obtain intimate mixing. This may be readily determined by visual-observation and is usually only a matter of three I I to five minutes, the exact duration of the mixing period usually being proportional to the viscosity of the oil.

It is not necessary that the resulting mixture be allowed to stand before filtering, but standing has the effect QfshOrtening filtration time. It is, therefore, preferred to allow a settling time, after mixing, of about, 5 to about minutes.

Before separating the suspended uranium values from the liquid phase in my invention, I find it advantageous,

but not critically significant, to raise the temperature of the, mixture. Raising the temperature results in a lowered viscosity of the liquid and permits more rapid separation of the liquid and solid phases, for example, by filtration. Thus a temperature of about 50 C. to' about 80 C. is generally found to provide optimum filtration results.

In carrying out the removal of uranium in accordance with my invention, approximately 1 part of acetone is intimately mixed with about 2 to about 12 parts of a hydrocarbon oil containing uranium as herein described, the resulting mixture allowed to stand for approximately 0 to approximately 15 minutes and filtered in a conventional manner. The resulting filter cake may then be washed with acetone, to remove any remaining oil, and then dried.

After treating various hydrocarbon oils in accordance with the above procedure, I find that they generally contain from less than /2 to about 5 parts per million uranium by weight, even when the initial uranium content of the oil may be as high as 25,000 parts per million.

The filter cake resulting from my process contains from about 0.3 to about 0.7 gram of uranium per gram of cake. The non-uranium portion of the cake not due to the anions associated with the uranium may result from the trapping, in the filtration step, of miscellaneous particles of dust, dirt, rubbish, carbon particles and metallic pieces that are present in the contaminated hydrocarbon oils. Thus, the results of the cake analysis for uranium is no criterion for the degree of success of my process, since the hydrocarbon oils that may be processed may range from an extremely clean oil, except for uranium content, to an extremely dirty oil.

The uranium in these cakes may be readily recovered simply by burning to the oxide and subsequent converting to the desired compound. For example, .the oxide may be fluorinated and the uranium recovered ,as UF vapors which are generally sufiiciently pure for process operations.

Sometimes, when treating a highly viscous hydrocarbon oil, my procedure may be facilitated by thinningthe oil prior to treatment with acetone. In this regard I have; discovered that, whereas the presence of carbon tetrachloride or trichlorethylene adversely afiects the action of acetone, a thinner comprising a relatively low viscosity hydrocarbon such as Varsol may be successfully employed. Thus, in certain instances, thinning vismay be achieved.

The following, specific examples illustrate my invention in greater detail:

Example I Two liters of hydrocarbon oil (Navy specification number 2075, viscosity at 100 R: 150-175 SayboltUniversal seconds, minimum flash point: 315 F., maximum pourpoint l0, F.,, maximum neutralizer number:

0.10) which had previously been exposed to gaseous UF and which contained approximately 22,000 parts per million uranium by, weight, was intimately mixed with one liter. of acetone by repeated, (5 times) pouring from one. vessel to another. The resulting approximate- 1y three-liter mixture was allowed to stand for 10 to 15 minutes, after which it was vacuum filtered with relative ease. The resulting filter cake was washed with acetone to remove any remaining oil and was then dried. Analysis of the filtrateindicated a uranium content of lessthan 5 parts per million by weight.

Example 11 The procedure of Example I was followed except that .1 liter of acetone was mixed with 11 liters of a hydro,-

carbon oil (pourpoint 20 F., flash point 410 F., visin accordance with my disclosure.

cosity .30 seconds at F., viscosity under 105, neutrality number 0.05) which contained parts per million uranium. Analysis'indicated that less than 5 parts per million uranium remained in the filtrate.

Example III The procedure of Example I was followed except that 1 liter of trichlorethylene was mixed with 2 liters of the above oil which contained about 19,000 parts per million uranium. Only a slight brown stain remained on a double filter paper after filtration. No reduction was noted in the uranium content of the filtrate.

Example IV About one liter of a tarry, greasy residue, resulting from exposure of the same type of oil utilized in Example I to ClF and contaminated with 15,000 parts per million uranium by weight, was diluted with 220 cc. of Varsol followed by intimate mixing with cc. of acetone. The resulting mixture was allowed to stand for three minutes and then vacuum filtered with relative ease. Analysis of the filtrate indicated a uranium content of less than 1 part per million by weight.

In general it may be said that the aboveexamples are merely illustrative and should not be construed as limiting the scope of my invention. Although the specifica tion is directed primarily to the treatment of hydrocarbon oils, my invention may also be applicable to less viscous hydrocarbon fractions such as kerosene and gasoline, and to more viscous hydrocarbon-containing materials such as greases. The latter, when in solid form, may be dissolved, with a relatively low molecular weighthydrocarbon such as Varsol, as herein disclosed for viscous hydrocarbon oils, thus permitting subsequent treatment The scope of my invention, therefore, should be understood to be limited only :as indicated by the appended claims. I

I claim:

1. An improved method of recovering uranium values from a uranium-contaminated hydrocarbon liquid which comprises contacting said hydrocarbon liquid with ace tone and separating the resulting solid uranium values from the resulting, substantially uranium-free, supernatant mixture.

2. An improved method of recovering uranium values suspended in a hydrocarbon liquid which comprises intimately contacting said liquid with sufficient acetone to fiocculate substantially all of said uranium values and separating the resulting solid uranium values from the resulting substantially uranium-free, supernatant mixture of acetone and hydrocarbon liquid.

3. The method of claim 2 wherein the uranium values consist of uranium fluorides.

4. The method of claim 2 wherein the uranium values consist of uranium tetrafluoride.

5. The method of claim 2 wherein the hydrocarbon liquid consists of a hydrocarbon oil.

6. The method of claim 2 wherein the uranium values consist of uranium tetrafluoride and the hydrocarbon liquid consists of a hydrocarbon oil.

7. The method of claim 2 wherein about 1 part of acetone is contacted with approximately 2 parts to approximately 12 parts of the hydrocarbon liquid.

8. An improved method of recovering uranium tetrafluoride suspended in a hydrocarbon oil which comprises intimately contacting approximately 2 parts to approximately 12 parts of hydrocarbon oil with approximately 1 part of acetone and separating the resulting flocculated uranium tetrafluoride from the resulting substantially uranium-free supernatant mixture of acetone and hydrocarbon oil.

9. The method of claim 2, wherein the hydrcarbon liquid has excess viscosity and is thinned with a relatively low viscosity, hydrocarbon liquid before the treatment with acetone.

10. An improved method of recovering uranium tetrafluoride suspended in a hydrocarbon oil which has been decomposed or polymerized into an extremely viscous mass, which comprises thinning said viscous mass with a relatively low viscosity hydrocarbon liquid until a readily flowing liquid suspension is formed, intimately contacting the resulting liquid with sufiicient acetone to flocculate substantially all of said uranium tetrafluoride, and separating the resulting solid uranium tetrafluoride from the resulting substantially uranium-free, supernatant mixture of said acetone, hydrocarbon liquid and hydrocarbon oil.

11. The method of claim 9 wherein approximately one part of the hydrocarbon liquid and approximately one part of acetone are used for approximately 5 parts to approximately 10 parts of the viscous mass.

No references cited. 

1. AN IMPROVED METHOD OF RECOVERING URANIUM VALUES FROM A URANIUM-CONTAMINATED HYDROCARBON LIQUID WHICH COMPRISES CONTACTING SAID HYDROCARBON LIQUID WITH ACETONE AND SEPARATING THE RESULTING SOLID URANIUM VALUES FROM THE RESULTING, SUBSTANTIALLY URANIUM-FREE, SUPERNATANT MIXTURE. 